Abstract
Toluene diisocyanate (TDI), a low molecular weight reactive chemical, is known
to be a main cause of occupational asthma (OA) in Korea. Although it is thought
that inhaled TDI may act as a hapten, the precise mechanisms of TDI-induced OA
are unknown. In this study, TDI-human serum albumin (HSA) conjugates (5, 10, 20
and 30 min) were prepared in the range of 1.5 to 5.0 TDI mole/HSA mole. Specific
binding of serum IgE to TDI-HSA (30 min) was observed using IgE ELISA as well as
ELISA inhibition assay. Around 40% of TDI-induced OA patients were positive for
serum specific IgE by ELISA. Degrees of serum IgE binding were different
depending on which TDI-HSA conjugate was used as an antigen. Moreover, binding
patterns were different depending on the individuals. Interestingly, higher
binding of IgE to TDI-HSA (5 min) than to TDI-HSA (30 min) which was more highly
substituted was observed in some patients. Probably new antigenic epitopes on
carrier proteins were targets of the specific IgE. The results of this study
indicated that IgE responses to TDI-HSA conjugates were heterogeneous in
TDI-induced OA patients and self-proteins modified by reactive chemicals can
become a major target antigen of IgE in certain cases.